United States Patent 5,141,752: Claim Scope, Expiration, and Osmotic Drug-Delivery Patent Landscape

U.S. Patent No. 5,141,752 covers a delayed-delivery osmotic dosage form. Its central combination is a semipermeable wall, an osmotically active drug compartment, a drug-free delay layer surrounding the drug formulation, and an outlet through which the drug is released. The patent issued on August 25, 1992, and its original 17-year patent term expired on August 25, 2009, assuming no unusual post-issuance adjustment. The patent therefore does not create current U.S. exclusionary rights.[1][2]

What does U.S. Patent 5,141,752 protect?

Claim 1 protects a dosage-form architecture rather than a particular active pharmaceutical ingredient. The claim requires the following elements:

Claim element	Required feature	Scope
A. Semipermeable wall	Wall admits external fluid but substantially blocks passage of the drug formulation	Covers osmotic membrane technology
B. Compartment	The wall surrounds and forms an internal compartment	Requires an enclosed dosage-form structure
C. Drug formulation	Formulation creates an osmotic pressure gradient across the wall and produces a therapeutic effect	Broad as to drug identity and therapeutic use
D. Delay mechanism	Drug-free lamina surrounds the drug formulation and delays release for up to 12 hours	The principal narrowing limitation
E. Exit means	At least one opening connects the compartment to the exterior	Requires a drug-release outlet

The claim is narrower than a generic controlled-release claim because it requires a drug-free lamina positioned around the drug formulation. It is broader than a drug-specific claim because it does not identify a particular active ingredient, disease, dose, release rate, or dosage strength.

The operative invention is a multilayer osmotic system. External fluid crosses the semipermeable wall, interacts with the osmotic formulation, and generates pressure. The drug-free lamina delays that process or delays communication between the osmotic engine and the drug formulation. Once the delay period ends, the system releases the drug through the exit means.

How should the claim be construed?

What is the scope of the semipermeable wall?

The wall must be permeable to an external fluid in the environment of use while being substantially impermeable to the drug formulation. The claim therefore targets membranes that permit water or another physiologically relevant fluid to enter but prevent the bulk drug composition from leaving through the membrane.

A membrane that freely allows the drug formulation to diffuse through it would not satisfy the claimed wall limitation. A membrane may still fall within the claim if it permits water ingress and blocks the drug formulation while the drug exits through a drilled, laser-formed, molded, or otherwise defined outlet.

The claim does not require a particular membrane polymer. Potential materials within the technical field include cellulose derivatives, cellulose acetate compositions, polyamides, polyurethanes, and other water-permeable polymers used in osmotic systems. The claim language itself does not limit the wall to one material.

What does “drug formulation” mean?

The claim uses broad functional language. The formulation must produce at least one physiological, pharmacological, local, or systemic effect in an animal. This language covers conventional pharmaceutical compositions and potentially veterinary products.

The formulation need not be a single active ingredient. It may include excipients, osmotic agents, binders, lubricants, stabilizers, and other components, provided the formulation functions as the drug-containing material and contributes to the claimed osmotic system.

What is the importance of the drug-free lamina?

The drug-free lamina is the most important structural limitation. It must:

Be drug-free in the sense required by the patent’s specification and claim construction;
Surround the drug formulation; and
Delay delivery for no more than 12 hours.

A dosage form that has a drug-containing core directly exposed to the osmotic driving force may not satisfy this claim if it lacks the surrounding drug-free delay layer. A coating applied only to the exterior of the dosage form may also fall outside the claim if it does not surround the drug formulation in the claimed internal relationship.

The claim does not state a minimum delay period. It covers a delay of less than 12 hours, including short programmed delays, as long as the delay is produced by the claimed drug-free lamina.

What does “at least one exit means” require?

The claim requires an opening or equivalent structure that communicates the exterior with the compartment. The outlet is the route through which the drug formulation is delivered.

The claim does not require one specific outlet geometry or manufacturing technique. A circular drilled hole, laser aperture, molded passage, or comparable opening may satisfy the limitation if it performs the required communication function.

Because the phrase “exit means” is functional, the claim may invite analysis under the means-plus-function provisions of 35 U.S.C. §112(f), depending on the construction applied by a court. Under that framework, the relevant structure would be the outlet structures disclosed in the specification and their statutory equivalents.[3]

Is claim 1 a combination claim or a broad platform claim?

Claim 1 is a combination claim with broad platform characteristics. It does not claim every delayed-release dosage form. Infringement would require the accused product to include all of the following in combination:

A semipermeable wall;
A compartment formed by that wall;
An osmotically active drug formulation;
A surrounding drug-free delay lamina;
A delay of up to 12 hours; and
An outlet communicating with the compartment.

The claim is potentially strong against products that copy the disclosed architecture. It is weaker against products using different delayed-release mechanisms, including:

Enteric coatings;
Matrix diffusion systems;
Reservoir systems without an osmotic pressure gradient;
Pulsatile systems using a soluble plug;
Programmable electronic pumps;
Coatings that delay release without a drug-free internal lamina; and
Multiparticulate systems that do not have the claimed wall-and-compartment structure.

What patents protect delayed-release osmotic drug delivery?

The relevant patent landscape includes several overlapping technology groups.

Technology group	Core concept	Relationship to U.S. 5,141,752
Basic osmotic pumps	Semipermeable wall, osmotic core, delivery outlet	Foundational technology
Push-pull osmotic systems	Expandable push layer drives drug formulation from a compartment	May avoid the claimed drug-free surrounding lamina depending on structure
Delayed-start osmotic systems	Release begins after a programmed lag period	Closely related technical field
Multilayer osmotic systems	Drug layer, push layer, barrier layer, and membrane	Potentially overlapping depending on the location and function of the barrier
Pulsatile dosage forms	Discrete drug pulses after a delay	May overlap if the delay is produced by the claimed drug-free lamina
Coated pellets and multiparticulates	Release controlled by particle coatings	Often outside the single-compartment architecture
Conventional matrix products	Drug dispersed in a polymer matrix	Usually outside the osmotic-wall limitation

The key distinction is structural. A product does not infringe merely because it provides delayed or once-daily release. It must use the claimed semipermeable osmotic architecture and the drug-free lamina surrounding the drug formulation.

When did U.S. Patent 5,141,752 lose exclusivity?

The patent issued on August 25, 1992. Under the pre-June 8, 1995 patent-term regime, the ordinary term for a U.S. patent was 17 years from issuance. On that basis, the patent expired on August 25, 2009.[1][2]

Event	Date
Patent issued	August 25, 1992
Ordinary statutory term	17 years from issue
Expiration	August 25, 2009
Current enforceability	Expired
Current Orange Book exclusivity	None based on this patent

The expiration removes the patent’s ability to block current manufacture, sale, use, or importation in the United States. It also eliminates the commercial significance of a present-day Paragraph IV challenge directed solely to this patent.

What is the Orange Book status of U.S. 5,141,752?

U.S. Patent 5,141,752 is a dosage-form platform patent, not a patent identified by a specific active ingredient or approved drug product. It therefore is not, by itself, the type of drug-substance, drug-product, or method-of-use patent ordinarily listed in the FDA Orange Book for a particular approved product.[4]

The Orange Book is organized around approved drug applications and the patents submitted for those products. A formulation manufacturer could have listed separate patents covering a specific approved product, but the existence of this broad osmotic patent does not establish an Orange Book listing for any named drug.

The practical result is:

No current Orange Book barrier arises from Patent 5,141,752;
The patent cannot support a current 30-month stay under Hatch-Waxman litigation procedures;
A generic applicant would assess any later-expiring product-specific patents separately; and
A platform patent’s expiration does not eliminate later patents covering a particular formulation, manufacturing process, dosage strength, or method of use.

Could this patent support a Paragraph IV challenge?

During its term, a generic applicant could have filed a Paragraph IV certification against an approved product if the patent had been listed for that product and the applicant contended that the patent was invalid, unenforceable, or not infringed.[5]

Because Patent 5,141,752 expired in 2009, a current Paragraph IV certification directed to this patent has no practical blocking effect. The patent cannot generate a 30-month stay against FDA approval. A generic applicant might still identify it in a patent-history analysis, but the patent would be treated as expired prior art or historical patent coverage rather than as a live barrier.

What generic-entry risks remain after expiration?

The expired patent reduces platform-level risk but does not eliminate product-level risks. Generic and follow-on manufacturers must still examine:

Formulation patents

A later patent may cover:

A particular extended-release profile;
A defined drug-to-excipient ratio;
A multilayer tablet;
A specific membrane composition;
A coating thickness;
A delivery aperture;
A defined lag time;
A particular salt, polymorph, or crystal form; or
A combination of active ingredients.

Method-of-use patents

A drug product may have later patents covering:

Treatment of a specified patient group;
A dosing interval;
A titration regimen;
A food-effect limitation;
A reduced side-effect regimen; or
A disease-specific use.

Those patents can create litigation or labeling issues even when the older osmotic platform patent has expired.

Manufacturing and process patents

Manufacturing barriers may involve:

Formation of the drug-free lamina;
Coaxial or multilayer compression;
Membrane coating;
Laser drilling;
Aperture inspection;
Osmotic-core fabrication;
Layer adhesion; and
Release-profile testing.

Process patents do not necessarily block an alternative formulation, but they can raise technology-transfer, freedom-to-operate, and supply-chain issues.

How strong is the patent estate for the claimed technology?

The historical estate was technically meaningful because it claimed a solution to a specific release problem: separating the drug formulation from the osmotic driving conditions through a drug-free delay layer.

Its strength can be assessed as follows:

Factor	Assessment
Active-ingredient breadth	Broad
Dosage-form breadth	Moderate
Structural specificity	High because of the surrounding drug-free lamina
Release-profile coverage	Moderate, limited to delays up to 12 hours
Design-around difficulty	Moderate
Current enforceability	None because the patent expired
Relevance to historical osmotic products	High
Current commercial blocking value	None

The claim could have been difficult to avoid for a product using the same internal multilayer concept. It was easier to design around by replacing the drug-free lamina with another delay mechanism or by using a different dosage-form architecture.

Which companies were most exposed to this technology?

The patent was associated with the Alza osmotic-delivery technology platform. Alza developed and commercialized multiple osmotic delivery systems and later became part of Johnson & Johnson.[6]

Potentially exposed commercial parties included:

Alza and its successors;
Licensees using Alza osmotic technology;
Drug companies commercializing controlled-release products under license;
Generic manufacturers copying an equivalent multilayer osmotic architecture; and
Contract manufacturers producing osmotic tablets or capsules.

The commercial value of the patent would have depended on whether it was practiced by a marketed product, whether that product generated substantial sales, and whether related patents remained in force. Patent 5,141,752 alone does not establish product revenue exposure.

What litigation and settlement risks remain?

Patent 5,141,752 cannot support a new infringement action because it is expired. Historical litigation may have involved related osmotic patents, product-specific patents, or continuation patents rather than this patent alone.

A current settlement involving an approved product would more likely concern:

Later-expiring formulation patents;
Method-of-use patents;
Drug-substance patents;
Polymorph or salt patents;
Manufacturing patents; or
Patent families claiming improved osmotic systems.

An expired patent may remain relevant as prior art in validity disputes involving later patents. It may also be cited in freedom-to-operate analyses to distinguish expired public-domain technology from live improvements.

Does biosimilar risk apply to this patent?

Biosimilar risk does not materially apply. Patent 5,141,752 claims a dosage form and drug-delivery mechanism, not a biologic molecule or biologic manufacturing process.

The relevant competitive risk is generic or authorized-generic entry for small-molecule products using controlled-release or osmotic delivery. Biologic applicants would instead assess composition-of-matter, formulation, device, manufacturing, and process patents under the Biologics Price Competition and Innovation Act framework.[7]

Key Takeaways

U.S. Patent 5,141,752 covers a delayed-delivery osmotic dosage form.
Claim 1 requires a semipermeable wall, an osmotic drug formulation, a drug-free lamina surrounding the formulation, a delay of up to 12 hours, and an outlet.
The claim is broad regarding the active ingredient but narrow regarding the internal dosage-form architecture.
The patent issued on August 25, 1992, and its ordinary term expired on August 25, 2009.
It has no current Orange Book blocking effect and cannot support a current Paragraph IV stay.
The patent does not create biosimilar risk.
Current freedom-to-operate analysis must focus on later formulation, method-of-use, manufacturing, drug-substance, and device patents.
The principal design-around options are replacing the drug-free surrounding lamina or using a non-osmotic delayed-release system.
The patent remains relevant as historical technology and potential prior art, but it has no present enforcement value.

FAQs About U.S. Patent 5,141,752

Does U.S. Patent 5,141,752 cover all once-daily drug products?

No. It covers a specific osmotic structure with a drug-free lamina surrounding the drug formulation. Once-daily release achieved through a conventional matrix, enteric coating, soluble plug, or other mechanism may fall outside the claim.

Is the drug-free lamina the same as an enteric coating?

No. The claimed lamina is an internal drug-free layer surrounding the drug formulation. An enteric coating is generally an external pH-responsive coating and does not automatically satisfy the claimed structure.

Can an expired osmotic patent block a generic launch?

No. An expired patent cannot independently block launch. A generic product may still face later patents covering the specific drug product, formulation, method of use, manufacturing process, or delivery device.

Does the 12-hour limitation mean the dosage form must release drug exactly 12 hours later?

No. The claim covers a delay of up to 12 hours. It does not require an exact 12-hour delay, although the product must meet the claimed structural and functional limitations.

Can a product infringe if its drug-free layer contains excipients?

Potentially. “Drug-free” does not necessarily mean chemically empty. The analysis turns on whether the layer contains no drug formulation as construed in light of the patent and whether it performs the claimed delay function. Excipients, osmotic agents, binders, or other non-drug materials may be relevant to that construction.

References

U.S. Patent No. 5,141,752, Delayed delivery drug dosage form (1992).
United States Patent and Trademark Office. (n.d.). Patent term calculator and patent term guidance.
35 U.S.C. § 112(f).
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
21 U.S.C. § 355(j); 21 C.F.R. § 314.94.
Johnson & Johnson. (2001). Johnson & Johnson completes acquisition of ALZA Corporation.
Biologics Price Competition and Innovation Act, Pub. L. No. 111-148, tit. VII, 124 Stat. 119 (2010).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	621030	⤷ Start Trial
Australia	7183787	⤷ Start Trial
Belgium	1000232	⤷ Start Trial
Canada	1297368	⤷ Start Trial
Switzerland	671696	⤷ Start Trial
Germany	3715224	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,141,752

Summary for Patent: 5,141,752